1. Field of the Invention
The present invention relates to a display driving circuit and a display driving system, and more particularly, to a display driving circuit having a half-VDD power supply circuit built therein and a display driving system including the same, in which the display driving circuit is further provided with a half voltage VDD terminal in addition to the highest voltage VDD terminal and the lowest voltage VSS terminal, and the half voltage, which is between the highest voltage and the lowest voltage, is generated and supplied by the half voltage power supply from the inside of the display driving circuit, rather than being supplied from an external power supply.
2. Description of the Related Art
A liquid crystal display is a device on which image data is displayed by passing light into a liquid crystal using the phenomenon by which the arrangement of the liquid crystal molecules varies depending on the applied voltage.
In the display driving circuit and system for driving the liquid crystal display, when current consumption, which is one of the most important factors, is increased, the temperature of the display driving circuit and system increases, and accordingly, the reliability and service life of the circuit and system can be degraded and shortened due to the increased temperature.
Thus, in the display driving circuit of the related art, an output buffer of the display driving circuit is further provided with a terminal of a half voltage VDD, which has a half voltage level between a first voltage VDD and a second voltage VSS, in addition to the first voltage VDD, having the highest voltage level, and the second voltage VSS, having the lowest voltage level, thereby reducing current consumption.
FIG. 1 is a block diagram illustrating the configuration of a display driving circuit in accordance with the related art, and FIG. 2 is a view illustrating a half voltage supplied from outside the display driving circuit of the related art.
Referring FIG. 1, the display driving circuit 100 includes a first buffer 110, a second buffer 120, a first switch 130 and a second switch 140.
The first buffer 110 is a buffer for driving a positive voltage level of a display panel, and includes a terminal of a first voltage VDD, having a high voltage level, a terminal of a second VSS, having a low voltage level, and a terminal of a half voltage H-VDD, having a half voltage level. In this case, the terminal of the half voltage H-VDD is connected to a discharging path of the first buffer 110.
The second buffer 220 is a buffer for driving a negative voltage level of the display panel, and includes a terminal of a first voltage VDD having a high voltage level, a terminal of a second voltage VSS, having a low voltage level, and a terminal of a half voltage H-VDD, having a half voltage level. In this case, the terminal of the half voltage H-VDD is connected to a charging path of the second buffer 120.
In addition, the half voltage HDD has a voltage level within a range between the first voltage VDD and the second voltage VSS, and allows the first and second buffers 110 and 120 to be operated.
Meanwhile, the first switch 130 is a switch for delivering input signals Even_input and Odd_input to the first and second buffers 110 and 120, and may be used for polarity inversion to prevent the phenomenon of adhesion of the liquid crystal display panel.
In addition, the second switch 140 is a switch for delivering output signals Even_output and Odd_output of the first and second buffers 110 and 120 to data lines of the liquid crystal display, and may also be used for polarity inversion to prevent the phenomenon of adhesion of the liquid crystal display panel.
As shown in FIG. 1, the buffers I10 and 120 according to the related art include the terminal of the first voltage VDD for operating voltage, the terminal of the second voltage VSS and the terminal of the half voltage H-VDD, that is, three terminals. Meanwhile, as shown in FIG. 2, when the display driving circuit of the related art is implemented, the first and second voltages VDD and VSS and the half voltage H-VDD are supplied from a power supply circuit on the outside of the driving circuit.
Thus, in the display driving circuit of the related art, since an additional power supply circuit for supplying the half voltage H-VDD must be provided on the outside of the display driving circuit, in addition to a supply circuit for supplying the first and second voltages VDD and VSS, there is a problem in that miniaturization of the system is difficult and production costs are increased.